Integrated circuits are required to operate over a large range of operational parameters, wherein operational parameters include, for example, temperature, humidity, power supply level and clock signal frequency. Many integrated circuits can properly operate at a certain combination of temperature, humidity, power supply level and frequency while fail at other combinations within the expected range of operational parameters.
Once a tested integrated circuit fails there is still a need to determine why it failed. This can involve determining which circuitry of the integrated circuit failed. Due to the complexity and size of modern integrated circuits this determination stage can be time consuming and very complicated. Typically, the analysis is based upon extensive knowledge of the design of the integrated circuit, the manner in which it has to operate and the like.
One prior art failure analysis method is known as latch divergence. Latch divergence uses a very long chain of latches within the integrated circuit. Data from this very long chain of latches is scanned out and compared to expected data values. This comparison can indicate which portion of the integrated circuit failed.
There is a need to provide efficient methods and devices for testing integrated circuits.